1. Field of the Invention
The invention relates to a chopper circuit that uses soft switching operation and a technique associated with the chopper circuit.
2. Description of the Related Art
In an existing art, in the field using a semiconductor power converter, a soft switching chopper circuit is used in order to reduce power loss (Japanese Patent Application Publication No. 2009-112182 (JP-A-2009-112182)).
Turn-on/off operations of a main switching element and auxiliary switching element of the chopper circuit are carried out in such a manner that gate signals that are turn-on/off signals are respectively transmitted from a control unit to both switching elements. The gate signals from the control unit are transmitted via a wire harness (WH), or the like, for signal transmission. However, there is a case where the gate signal is not input to the auxiliary switching element because of a break in the wire harness, an external noise, or the like, and then the auxiliary switching element does not operate. In this case, as the main switching element operates, there is a possibility that a voltage applied to the main switching element increases to cause the switching operation of the main switching element to become hard switching, resulting in a breakdown.